Pin-type coupling



Aug. 23, 1949. A, BERTEA 2,479,807

PIN-TYPE COUPLING` Filed Dec. 18, 1947 IN VEN TOR. A/f/c 5.6/2 754Patented Aug. 23, 1949 UNITED STATES PATENT FFICE PIN -TYPE COUPLINGAlex Bertea, Pasadena, Calif. Appiication December 18, 1947, Serial No.792,504

3 Claims. 1

My invention relates to pin-type couplings, and has particular referenceto a pin-type coupling permitting small lateral displacements of thecoupled members.

In the design and manufacture of many mechanical parts and machines itis necessary to make surfaces concentric. This is not ordinarily aproblem when tolerances are ample with respect to the machine toolsavailable, particularly when the two surfaces are formed on a singlepiece of metal or other structural material. The problem becomes acute,however, when the tolerances are minute and the concentricity must beestablished between two separate parts that are joined together.

For example, in constructing hydraulic actuating cylinders for aircraft,especially for high pressure (3,000 to 5,000 p. s. i.) systems, thetolerances are necessarily minute to prevent leakage and to insuresatisfactory operation. Further, it is necessary or desirable to machineseparately the barrel and the end caps of cylinders, and accordinglythese end caps are threaded to a tubular barrel to form the cylinderhousing. The piston within the barrel and the piston rod passing throughan end cap are necessarily concentric, requiring that the interior ofthe barrel and the bore for the piston rod be concentric within atolerance of several ten-thousandths of an inch.

While expert machinists employing precision machine tools can hold suchtolerances, it is uneconomic to hold these tolerances for large quantityproduction. The forming of threads on the barrel that are concentricwith the inside diameter and the forming of threads on the end cap thatare concentric with the piston rod bore give rise to four separatepossibilities wherein concentricity error may occur. My presentinvention avoids the entire problem of concentricity tolerances anderrors by providing a, coupling between piston rods and pistons and likeconcentric parts that provides for lateral discrepancies inconcentricity. Accordingly the threads on the barrel may be slightlyacentric with respect to the inside diameter, and likewise on the endcap the threads may be acentric with respectto the piston rod bore, andvice versa. Further, angular discrepancies between the barrel insidediameter and the piston rod bore may be accommodated.

The resulting eiciencies in mass producing precision parts are obvious.The threads and bores may be accurately formed with good qualitymachines, with the primary attention being directed to the particularmachining operation being performed. Minor acentricities, however,

will not result in the scrapping of valuable components which may havereceived several hours of expensive precision machining and iinishing inaddition to the initial material and forming cost. Also the parts joinedby my coupling construction are strongly interconnected by a long-lifemechanism.

It is therefore an object of my invention to provide an improvedpin-type coupling permitting lateral displacements of the coupled parts.

Another object of my invention is to provide a pin-type coupling forparts normally concentric, but accommodating reasonable concentricitytolerances.

Another object of my invention is to provide an improved pin-typecoupling that is inexpensive to manufacture and which accommodatesconcentricity discrepancies.

Other objects and advantages of my invention will be apparent in thefollowing description and claims, considered together with theaccompanying drawings, in which Fig. 1 is a sectional View through anillustrative actuating cylinder wherein the piston and piston rod areinterconnected by a coupling construction embodying my invention;

Fig. 2 is an exploded' perspective view of the coupling of Fig. 1;

Fig. 3 is a plan view of the coupling of Fig. 1; and

Fig. 4 is an enlarged sectional view through the tubular member of thecoupling illustrating the manner in which a milling cutter may beemployed to aperture the tube.

While I will describe my invention with respect to an actuatingcylinder, it will be obvious that it is applicable to various othertypes of machinery and apparatus. For example, in the aircraft hydraulicline it is applicable to the slide valves, hand pumps, and other similarmechanisms using a sealed rod passing through a wall of a housing.

Referring to Fig. 1, there is illustrated a fragmentary hydraulicactuating cylinder I0 including a barrel II having an end cap I2 securedthereto as by a threaded connection I3. Hydraulc fluid under pressuremay be introduced into the cylinder by any suitable means, for exampleby a fitting not shown, and leakage of this uid through the thread jointI 3 may be prevented by an O-ring seal i4 which for example may bedisposed in the end cap i2.

Sliding within the barrel I I may be a piston I5 connected to a pistonrod I6 which passes through the end cap I2 by means of a bore I'i.Leakage of iluid around the piston rod I6 is pre- 'vented by an O-ringI8 disposed Within an intermediate portion of the bore I'I.

In the actual production of the hydraulic cylinder I0, the interior boreI9 of the barrel I I will be iirst machined and then later honed orburnished to a mirror iiinish. The threads are normally formed on thebarrel II prior to the mirror ilnishy but Whether they are formed beforeor4 after the finishing of the bore I9, it is almost agcertainty thatthere will be a concentricity error between the threads and the bore ofat least a few ten-thousandths of an inch, and ordinarily severalthousandths of an inch, re-

gardless of the care exercised. Nor can modern honing machines correctfor any such discrepancies in concentricity Without undue complicationof operation. Likewise the piston rod bore I'I must be concentric withits threads, but here again there is the certainty of a concentricitydiscrepancy ofappreciable dimension, regardless Qofthe .careexercisedThese acentricities are ac- ,COmmOdated however, by my pin-typeconnection 'employing as the joining medium a pin 2 I .flnforming the pincoupling, I prefer to make lonefoffthe joined. members in tubularform, for example by providing the piston i5 With a tubularprojection,22. The other member may telescope 'thie'n'aiid he. suitablyapertured to receive the pin'ZI. For example, vthe piston rod I6 may beY bored aslat"23....Whileit Would seem permissible touse a plain pn'ofVround cross section and use merelyoversize' holesfinthetube 22 and inthe bore 23, this is'not ordinarily acceptable, inas- JnuC-h as .thereWillbe considerable slap and play Y in the connection which is not onlynoisy, but `providesan undesirableA element of lost motion. Accordingly,therefore, .I have devised my pintype coupling so that .the lost motionis practioally eliminated andso thatthere will be little slap or noisein thefconnection.

In accordance with my invention, I aperture .the tubular member 22 attwo diametrically op- -gposed points 26 by means of milling cuts illus-Ltrated. in Fig. 4.v Accordingly a milling cutter 25 may be movedagainst the tubular member 22,

YYmilling a Vpair of` axially transverse slots therein, as

illustrated in Fig. 4. rIhe pin 2i isgenerally round in cross section,but itis provided with a pair of flats 26 on opposite sides thereof thatt closelythe straight Walls ofY the slots 24. Asillusvvtrated in Fig. 3,the length of the milled apertures 24 is somewhat in excessof thediameter of the pin 2|, allowing the pin to move laterally.

The bore 23 in the piston rod I6 as illustrated in Fig. lappears to begreatly oversize with respect to ,thepin 2 I., but it will be noted thatthe pinli isY beingrviewed from its side or least dimensional aspect,and that actually the bore 23 may be one-V or tWo-thousandths of an inchundersize with respect to the pin 2l so as to 'obtain a drive or pressiit between the. bore and the pin. The drive rit not onlyY .eliminates a.possible backlash factor, but also securely positions the pin in thecoupling parts. To facilitate the drive lit, the ends of the bore 23 maybe countersunk as Vat 2 so that only the center part of the shaft I6actually bears against the pin 2I. `Acentricities along a vertical linemay be ac- -conimodated by the pin 2I sliding up or down in the milledslots 2A, as is obvious from an inspection of Fig. 1. Acentricities in ahorizontal or lateral direction may be accommodated by movement of the-pin 2| transverse to its axis because the excess of the length of theSlots 24 over Yclearance on each side ofthe pin 2l.

'4 the diameter of the pin 2|. Accordingly, therefore, acentricities ofany lateral disposition may be accommodated by any combination of thesetwo movements.

The pin 2| may be maintained in its milled slots 24 by its drive iit onshaft I6, but I prefer also to employ a lock Wire 28 passing throughsuitable apertures 29 in each end of the pin 2|.

`It.will-benotedithat thesewire Aapertures 29 are vdisposedVconsiderablyirnitward` of the bottom of the mill cuts 24, and henceallow the pin 2| to move along its axis.

The size of the aoentricities to be accommodat- Ted will? govern therelative sizes of the different iFor example, if it is decided thattolerances for acentricities off ve-thousandths of an inch arepermissible, then the length of the aperture 24sho`uld permitve-thousandths of an inch of Likewise 'the diierence between theoutsidev diameter Yof thepiston rod l'and the inside diameter of thetube 22 should permit ve-thousandths of an inch clearance on each side.

If thepin structure is to be employed in a slide valve, flow may takeplace through the tubular member 22 by providing a series of ports 3ladjacent the inner end ofthe rod I6. Accord- Vingly,thereforemycouplingstructure need not interfere with uid ow, if for anyreason this is desired. y 1

l In operationlfhiy coupling maybe assembled prior to the-Iclosure/,of-Vthe`- end cap I2 on the cylinder barrel II. Acentricities will beaccom- Irledetedby movement of ihepin 2 I. up and down 'in the Slots .24.1h @ademend byhaving the vpin .'2I .move in its ape'rtures24 in theother dimension.'V 'Thejsolid `bearing ofthehflats 26 of thepinagainstuthef-wallsrofthe'umill cuts 2li gives a good `forcetransmission surface, in addition to eliminating end'play Yorlostmotion. The driven@ bearing of the rodgleon the pin is by thecircular grasp A on nthe Nroundedl Vportions of thepin, thuseliminatin'glany end play here.

While I have desnbeeiny 'invention with respect to a specic embodimentthereof, I do not 'limit 'myself to this embfqdiment, since it is .0b-

vious that various modifications could be made therein WihglldepftngITIII the, true spirit and scope of'wrnylinventipn. j Accordingly thedisclosed embodiment is merely illustrative and not deiinitive.

Iclaim: f

1. A pin-type',couplingbetweena tube and a member telescopingwithin atube comprising: diametrically opposed' mill cuts on the tube that'aperture the tube; a pininsertable through the tube mill fout aperturesand having a generally round cross section with opposite sides ilatted,the two piniiats being adapted to lie against the opposite edges ofthenjlill out; ancla bore through the member having afdiameter slightlyless than the pin diameter, whereby the pin may have a drive fit in thebore and the iiats of the pin give a sliding bearing on the tube. A

2. A pin-type coupling comprising: a tubular member; a shaftadapted totelescope therein; diametrically opposed mill cuts on the tube disposedaxially transvers'e thereof to define straight sided apertures; aborethrough the shaft; anda pin disposed in the cuts andpassing throughthe bore and having opposite sides latted to bear against the straightsides of the mill cut apertures; 'v

3. A 'pin-typecouplin'g comprising: a Vpin having a generally roundedcross section but having opposite sides ilatted; a tube havingtransverse diametrically opposed mill cuts of a width equal to theflatted dimension of the pin and forming apertures of greater lengththan the pin diameter; and a rod disposable within the tube and havingan outside diameter less than the inside diameter of the tube and havinga pin receiving bore therethrough that is slightly less than the pindiameter, whereby acentricities may be accommodated by movement of thepin length- 10 Number REFERENCES CITED The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS Name Date 1,107,881 Berntsen et al Aug. 18, 1914

